(1) Field of the Invention
The present invention relates to therapeutic medical apparatus systems, delivery systems, devices and/or methods, and to apparatus and methods for using neural stimulation to alleviate the symptoms of movement disorders, such as those associated with Parkinson's disease, essential tremor, dystonia, and Tourette's syndrome, including tremor, bradykinesia, rigidity, gait/balance disturbances, and dyskinesia, and also for treating mental health disorders such as major depression, bipolar disorder, and obsessive compulsive disorder for example. The present invention further relates to the use of a movement disorder diagnostic device for manually, semi-automatically, or automatically adjusting therapeutic systems, devices, delivery systems, as well as methods thereof.
(2) Technology Review
A current trend in the treatment of diseases identified as being associated with the central nervous system is the stimulation of target areas of the central nervous system to affect therapeutic benefit. Such stimulation has been accomplished with, for example, implanted electrodes that deliver electrical stimulation to target brain regions; one class of electrical neural stimulation devices has been categorized under the name “deep brain stimulation” (DBS). Although the exact neurological mechanisms by which DBS therapies succeed are complex and are not yet fully understood, such therapies have proven effective in treating Parkinson's disease motor symptoms (such as tremor, bradykinesia, rigidity, and gait disturbances), and investigation into the use of DBS for the treatment of this and other neurological and mental health disorders, including major depression, obsessive-compulsive disorder, tinnitus, obesity, criminal tendencies, and antisocial disorders, is ongoing.
Parkinson's disease (PD) affects the motor system and can be characterized by motor symptoms including tremor, bradykinesia, and impaired gait. When diagnosed, dopamine replacement medication is prescribed. However, over time drug effectiveness decreases, requiring increased dosage. Frequent and stronger side effects such as dyskinesias (uncontrolled, irregular movements) and unpredictable “on”/“off” episodes are cause for more invasive intervention. Deep brain stimulation (DBS) surgery is performed when medication no longer adequately treats symptoms. Significant costs are not only associated with the initial implant surgeries (˜$40,000), but also subsequent stimulator battery replacements (˜10,000-20,000), outpatient programming sessions (˜$1,000), and geographic disparities can put a significant financial and emotional burden on patients over many years, especially if the expected therapeutic improvement is not achieved. Although DBS has become a standard of care for many advanced stage PD patients, post-surgical outcomes are not equal across patients. A University of Florida study followed over 100 DBS patients, primarily PD, seeking referral to their movement disorder specialist after experiencing unsatisfactory improvement. Of those patients, 28% had been misdiagnosed presurgery and 90% had unsatisfactory symptomatic benefit including 40% for tremor, 37% gait, 11% for motor fluctuations and dyskinesias, and 14% for bradykinesia. The study also strongly argues for the need of preoperative education to ensure appropriate referral and selection of DBS candidates.
As a result, there are no set criteria for surgical patient selection. Subjective screening questionnaires have been developed to determine appropriate candidates based on a significant levodopa response (greater than 25%), the presence of motor fluctuations and dyskinesias, and minimal to no cognitive decline. However, methods to accurately evaluate these criteria are severely lacking for several reasons. First, the pattern and severity of motor symptom and dyskinesias vary greatly throughout the day. Therefore, an in-clinic assessment over multiple medication dose cycles is not feasible and is conducted under artificial conditions. Patients are typically asked to come in OFF PD medications from the previous night. Long travel days and pain and stress associated with being in this therapy state may induce fatigue and increased symptom severity. Second, clinical rating scales, most commonly the Unified Parkinson's Disease Rating Scale (UPDRS), are used to evaluate ON and OFF PD symptom states. Under the UPDRS, symptoms are subjectively rated on a 0-4 scale corresponding to normal, slight, mild, moderate, and severe, which can suffer from poor inter- and intra-rater reliability. An alternative, using home diaries, relies entirely on the patient's perception of their medication state and their level of compliance. Patients may also underestimate dyskinesia and motor symptom severity and have difficulty distinguishing between dyskinesia, tremor, and normal voluntary movements, a situation that can make evaluating medication response particularly challenging. Third, limited work has been conducted to directly compare pre-surgery medication response with post-surgery outcome in order to better select DBS candidates.
Access to movement disorder specialists to undergo the subjective screening questionnaires may require many clinical visits and can be financially burdensome for the geographically disparate subset of the PD population or those unable to travel. Movement disorder center locations can limit access to well-trained clinicians and effective symptom management. Rural patients in one study had a significantly worse quality of life score than their urban counterparts. Telehealth technologies such as home monitoring and online patient data management can have a significant impact on the equity, accessibility, and management of PD for patients who live in rural and remote communities or those unable to travel. In particular, one study showed that over a three-year period, telemedicine used for 100 follow-up visits for 34 PD patients left patients and providers satisfied with use of the technology and their savings amounted to approximately 1500 attendant travel hours, 100,000 travel kilometers, and $37,000 in travel and lodging costs. Typically, medication for Parkinson's disease (PD) consists of Levodopa to alleviate symptoms. Over time, however, the medication has reduced efficacy and shows increased occurrence of side effects such as dyskinesias. Once side effects outweigh benefits, patients consider deep brain stimulation (DBS). An electrode/wire lead is implanted in a specific location in the brain which shows hyperactivity in PD patients and is sensitive to electrical stimulation. PD target sites are the subthalamic nucleus (STN) or globus pallidus internus (GPi). The Essential tremor and Parkinson tremor target site is generally the ventral intermedius nucleus of the thalamus (VIM). Electrical pulses characterized by amplitude (volts), current (amps), frequency (Hz), and pulse width (microseconds) are regulated by an implantable pulse generator (IPG) placed beneath the skin on the chest. Stimulation affects motor symptoms on the contralateral side, i.e., right side tremor will be treated on the left brain. After a patient has been implanted and recovered, programming sessions will fine tune stimulation settings described above in order to minimize symptom severity, minimize side effects, and maximize IPG battery life span. Although medication is not eliminated, it is typically reduced significantly. DBS efficacy decreases over time as the body adjusts to stimulation and protein buildup around electrode lead attenuates electrical field. Programming sessions are required throughout the patient's lifetime, though the frequency of adjustments is typically greater at first.
A typical implanted DBS stimulation lead consists of a thin insulated needle comprising four platinum/iridium electrodes spaced 0.5 or 1.5 mm apart along the length of the lead. One or multiple leads may be implanted in a target brain region or regions to provide symptominhibiting high-frequency stimulation, although some research suggests that excellent results can be achieved even when the lead is implanted distant from a target region. A DBS lead is connected to an implantable pulse generator (IPG), which serves as a controller and power source, via an extension cable tunneled subcutaneously to a subcutaneous pocket in the chest or abdominal cavity. The IPG typically includes a battery and circuitry for telemetered communication with an external programming device used to adjust, or “tune,” DBS stimulation parameters, which may include but are not limited to stimulation frequency, amplitude, pulse width (or wavelength), waveform type, and contact configuration (that is, the selection of which electrodes are utilized from among the electrodes available on a lead, and, if two or more electrodes are active, the relative polarity of each), and the like. These parameters are initially set during implantation surgery separately and independently for each DBS lead that is implanted, and are then further fined-tuned in the outpatient clinic or in a doctor's office following surgery to maximize therapeutic benefit and minimize undesirable stimulation-induced side effects. The first such programming session usually takes place several weeks following implantation surgery, after the patient has recovered and inflammation at the lead placement site has subsided.
DBS programming may be performed by movement disorder neurologists, neurosurgeons, fellows, occupational and physical therapists, nurses, or employees of the DBS manufacturer. However, many patients have inadequate access to DBS programming due to physicians and patients relocating as well as implantations occurring at facilities far from a patient's home. Additionally, there is a shortage of health care professionals highly trained in DBS programming. This can partially be explained by a reluctance to participate in DBS management due to a lack of familiarly with electrophysiology or possibly the costs associated with postoperative DBS management. Retrospective studies found that DBS programming sessions take more than twice as long as typical evaluations by movement disorder neurologists. Furthermore, programming sessions must be limited to 1-3 hours since longer sessions result in patient fatigue or lightheadedness. Multiple visits lead to additional travel costs and can be particularly difficult for those traveling from rural areas.
The approaches to programming can vary greatly across institutions. Strict iterative procedures whereby initial subjective test results based on human observation are used to determine the effect the parameters have of the patient and new parameters are determined based on those results by clinician calculation and observation are quite time consuming and therefore rarely followed. Many programmers make educated guesses as to the best settings based on their prior experience; however, this experience can vary across institutions and may not take into account varied lead positioning. Many programmers simply ignore bipolar or tripolar configurations whereby stimulation is provided from two or three contacts on a single DBS lead simultaneously, and do not adjust frequency or pulse width in an attempt to speed the programming process; however, neglecting these options can lead to suboptimal patient outcomes. Many clinician programmers do not fully appreciate the different programming parameters or modes of stimulation. In constant-voltage IPGs, the voltage of each pulse is set, but the current will automatically change based on the electrode impedance. This leads to variable amounts of current being delivered the stimulation target as impedances change. Additionally, since impedances will vary across electrode contacts, applying the same voltage on two different contacts will likely lead to different therapeutic currents being delivered. On the other hand, constant-current IPGs specify the current to be delivered and adjust the voltage accordingly based on the impedance. Since the therapeutic effects of DBS are based on current delivered at a given target, constant-current IPGs are preferable to constant-voltage IPGs.
While the above-described equipment and procedures are typical as of the filing of this application, variations and refinements may become commonplace as neural implant technology advances. Conceivably, uses of a multiplicity of DBS leads or networks of DBS leads may provide greater coverage, enabling the stimulation of larger and more varied target areas, and miniaturization and improved telemetry may obviate the need for the extension cable and/or the IPG altogether as leads become self-powering and/or self-controlling or permit for built-in telemetry. Advances in nanotechnology and materials may also allow DBS leads in the future to become self-repositioning, self-cleaning, or resistant to biological rejection for improved long-term therapeutic operation and more precisely targeted implantation.
The current standard in evaluating the severity of movement disorder symptoms in Parkinson's disease is the manually human scored Unified Parkinson's Disease Rating Scale (UPDRS) used to score motor tests, many of which involve repetitive movement tasks such as touching the nose and drawing the hand away repeatedly, or rapidly tapping the fingers together. A battery of exercises, typically a subset of the upper extremity motor section of the UPDRS, is normally completed during DBS lead placement surgery and subsequent programming sessions to evaluate performance while a clinician qualitatively assesses symptoms. Each test is evaluated by a clinician based solely on visual observation and graded on a scale that ranges from 0 (insevere) to 4 (severe).
During DBS implantation surgery, various lead placement strategies are used, including inversion recovery imaging, reformatted anatomical atlases, and formula coordinates based on known landmarks. Implantation location is verified and adjusted based on electrophysiological mapping using techniques such as microelectrode recording and micro and macro stimulation. Currently, lead placement and stimulation parameters are modified based on subjective motor examinations such as clinical observation such as the UPDRS motor tasks during the implantation procedure. After lead placement, patient motor symptoms are evaluated in response to a set of stimulation parameters. Stimulation parameters are then adjusted, and motor exam repeated. This trial-and-error process of adjusting parameters and monitoring patient response is continued until an optimal electrode position and stimulation set are established. During this programming or “tuning” process, the clinician subjectively assesses motor symptom improvement.
Postoperatively, assessing DBS response and reprogramming stimulation parameters require a significant time commitment. Several stimulation parameters can be modified, including electrode polarity, amplitude, current, pulse width, waveform type, and frequency. DBS programming and patient assessment may be performed by a variety of healthcare professionals, including movement disorder neurologists, neurosurgeons, fellows, occupational and physical therapists, nurses, and employees of the DBS manufacturer. Stimulation optimization is typically performed based on results of an exam such as the UPDRS, with the patient in four states (off medication/off DBS, off medication/on DBS, on medication/off DBS, and on medication/on DBS). The process of DBS adjustment is iterative and largely involves trial-and-error. Programming and patient assessment from preoperatively to one year after surgery requires approximately 30 hours of nursing time per patient.
Clinicians presently lack tools that combine physiological, electrical, and behavioral data to optimize electrode placement and stimulator programming. Optimizing electrode placement and stimulation parameters improves patient outcome by alleviating motor symptoms and minimizing complications. The present invention addresses this need for improved electrode placement and adjustment of deep brain stimulation parameters by providing a repeatable, automated or semi-automated tool that can assist stimulation parameter tuning during surgical electrode placement and outpatient programming sessions. In particular, the present invention aims to provide methods for the collection and transmission of objective biokinetic data during these procedures, which data is then processed to output objective movement disorder symptom severity measures on a continuous scale in real-time to guide clinician decision making. The improved resolution and repeatable results of the present invention should reduce time and costs of DBS procedures as well as improve patient outcomes.
It is therefore an object of the present invention to provide a system for screening patients for viability of DBS therapy prior to extensive, repetitive travel and expense, and prior to requiring surgical implantation of DBS leads. It is further an object of the present inventions to provide such a screening system to help minimize healthcare costs and to prevent adverse effects in patient quality of life associated with ineffective or unnecessary surgery, and to help clinicians to better select courses of treatment for patients.
It is further an object of the present invention to couple at-home patient viability screening and automatically-assigned quantitative motor assessments with procedures and practices for DBS implantation and parameter tuning and programming in semi-automatic and automatic ways to provide improved and less costly movement disorder patient therapy.
It is further an object of the present invention to provide automated functional mapping based on objective motor assessments and algorithms for resolving an optimal set of programming parameters out of the thousands of possibilities to provide an expert system to enable programming at a local medical facility. The system is designed for use by a general practitioner or nurse rather than by a neurologist or neurophysiologist with years of experience in DBS programming and disease management to increase access to high-quality postoperative DBS management. The system will minimize the required expertise of the clinician by requiring little or no advanced knowledge of complex neurophysiology or MRI imaging.
Existing systems for quantifying Parkinson's disease motor symptoms are described in this application's parent application, U.S. patent application Ser. No. 12/250,792, which is herein incorporated by reference, and which describes a novel system for measuring motor dysfunction symptoms and computing measures based on UPDRS scores therefrom. Preferably, the system and methods described therein are incorporated, in whole or in part, into the present invention as a means of automatic symptom quantification. The resultant scores objectively quantify movement disorder symptoms advantageously using a scale that is familiar to clinicians.